Use Of Mechanical Tests Research Articles

Joint Quality Assessment of Ultrasonic Metal Welded Parts by Fracture Surface Evaluation

In ultrasonic metal welding, low specific resistances and large joining surface cross-sections require the use of mechanical testing to quantify the joint quality. In this study, different quality features of ultrasonically welded joints made of pure copper sheet are investigated during the successive phases of joint formation. Two test series with different workpiece geometries are examined. It is shown that mechanical quality features such as shear and peel forces behave differently over the formation of the joint and are not transferable. As an alternative to these, laser scanning microscopy is used to record images of the fracture surface that describe the growth of the joint area during formation. The study finds that shear tensile force growth and joint area growth are non-linear and comparable, with optimized welds achieving joint areas of 30 mm2 out of 64 mm2 and 6 mm2 out of 16 mm2. Although overall quality increases with increasing welding time, the material strength in the joint zone decreases. Depending on the original rolling condition, between 43% and 59% of the original material strength can be identified as the joint strength. The automatic analysis of fracture images is a suitable alternative to mechanical testing for similar joints.

Influence of index properties on the cyclic failure of fine-grained soils

The purpose of this study is to develop an easy procedure to diagnose the cyclic behavior of fine-grained soils, leading to liquefaction.There are approaches to this problem with reference to liquid limit (wL), plasticity index (PI), clay content, (C%), in-situ water content compared to the liquid limit (wn/wL), average grain size (D50), and liquidity index (IL). Previous research has indicated that fine-grained soils defined as “sand-like” are prone to liquefaction. There is consensus that liquefiable silty soils have “sand like” characteristics. In the transition from sandy to clayey, it is generally accepted that it would be appropriate to make a judgment by making use of mechanical testing and that clayey soils do not liquefy.This paper presents the results of dynamic triaxial shear testing (CTX), where excess pore water pressures and axial strains are evaluated compared to the physical properties to reach the threshold for cyclic failure. Samples of undisturbed soil procured from different locations of the city of Adapazarı, Turkey, were subjected to CTX testing. The results were interpreted in the light of the physical properties to arrive at a judgment of cyclic failure.Being able to identify a liquefaction prone fine grained soil by merely measuring a few physical properties without resorting to arduous cyclic testing would be an advantage to the practising engineer. This however necessitates the elimination of the ‘gray zone’ for which most researchers recommended the use of cyclic testing.The main finding of this study is that samples reaching double strain amplitude (DSA) of <5% in the CTX test contain no sand and have a clay content of 20% or more. An attempt to establish a relationship between sensitivity to cyclic loading and physical properties is also made.

Aging Modeling of Low-Voltage Cables Subjected to Radio-Chemical Aging

This article presents the development and application of a modelling approach based on quantities obtained from mechanical and electrical tests to assess the aging of low voltage cable insulation for nuclear applications. In order to obtain experimental data needed for the establishing of the models, accelerated aging is performed on coaxial cables. The first part of this paper focuses on the development of a predictive modelling for mechanical properties; this allows the evaluation of the Dose to Equivalent Damage (DED) as a function of the aging stress (dose rate). However, the use of mechanical tests for cable aging assessment presents some problems, being such tests destructive for the insulation and potentially affected by local defects. The novelty of this work lays on the introduction of a new model, allowing the definition of the end-of-life point in terms of electrical non-destructive tests. The second part of this article presents the development of aging modelling of cable insulation and correlation with experimental data obtained at different stresses, which allow the estimation of the expected life of the cable under test to be derived from diagnostic measurements of electrical properties like, e.g, tan δ. Finally, the application of the proposed life model to two typical real-condition nuclear environments is presented and discussed.

The Use of Mechanical Testing, Photomicrography, and Electron Microscopy to Characterize an Insulating Fiberglass Composite Post-Electrical Arc Failure.

The Use of Mechanical Testing, Photomicrography, and Electron Microscopy to Characterize an Insulating Fiberglass Composite Post-Electrical Arc Failure.

A procedure for a mechanical evaluation of an undefined osteo-protective material

Falls represent a major care and cost problem to health and social services world-widely, since 50% of falls result in an injury. In this work, is proposed a methodology to evaluate protective pads materials and geometry performance, in order to reduce impact results in a fall event. Since the material properties and the pad geometry are the key factors to make the protection possible when a fall event occurs, our approach relies on the use of mechanical tests to evaluate the properties of the material and in the study of the pad response during a fall. For this, were used compression, tensile and instrumented falling weight tests, that allow a fully characterization of the materials that can be employed in the protective pads. Likewise, to gather precise information on falls events, in order to study the pad response during a fall, a set of laboratory fall trials were created using a camera-less inertial motion capture (mocap) system. This allow the acquisition of dynamic information of falls, namely acceleration and velocity that can be used to create a finite element analysis (FEA) model, where different segments from the human body can be evaluated when the protective pad is associated to it. Through the proposed methodology, different materials and pad geometries can be studied towards maximizing the performance of protection pads for falls. The mocap system allows the acquisition of fall data, and also the creation of a human body geometrical model, representative of the fall. From the mechanical trials, was showed that the spacer fabric embedded with silicone has the higher ability to reduce the peak force in case of impact when compared with all the other specimens. The compression and the tensile tests allow the mechanical definition of the material, and with this the material definition on the FEA model.

Characterization and Cell Response of Novel Hydroxyapatite/Glyceride-Based Polyurethane Porous Scaffold

The glycerides of castor oil (GCO) were copolymerized with isophorone diisocyanate (IPDI) to generate glyceride-based polyurethane (GCPU), meanwile blending with hydroxyapatite (HA) powder to fabricate porous composite scaffolds. The effect of HA content on mechanical properties of the resulting polymer scaffolds and the in vitro cell response of HA/GCPU scaffolds were investigated, by use of mechanical testing, FTIR, SEM and MTT assay. The results showed that the compressive strength increased with HA content, and the HA/GCPU scaffold with 40 wt% HA reached about 4.6 MPa, much higher than the scaffold without HA (only 605 kPa). The SEM observation, live-dead staining assay and MTT assay demonstrated the excellent biological properties of HA/GCPU scaffolds, which support cell adhesion and proliferation. This novel class of HA/GCPU porous scaffolds have prospect and advantage for bone repair and regeneration.

S022025 髄内釘の開発・評価におけるFEM解析と力学試験の相互関係について

Today the development of most orthopedic implants makes great use of Mechanical testing and FEM analysis. At Mechanical testing however, it is difficult to know about the conditions within implant and results are prone to error. Additionally, in FEM analysis, results can change even when something as simple as boundary conditions are chosen incorrectly. In this study, the evaluation of mechanical and FEM analysis using an intertrochanteric femur fracture model was performed. An intertrochanteric femur fracture fixed with a femoral nail was first designed in CAD software. The mechanical model was tested under single compression and the displacement deviation between before and after compression was measured with a contactless 3D-Scan. In the FEM analysis, constraint conditions were defined similar to Mechanical testing conditions. Displacement was used to compare the results. The deformation method of the mechanical test was similar to that of the FEM analysis. However, displacement values of the FEM analysis were twice than the mechanical displacement. The elastic modulus of the inner urethane foam duplicates cancellous bone changes because the applied loads crumpled air holes within the urethane foam. The results of the FEM analysis will differ from Mechanical testing due to the fact that the elastic modulus used for FEM calculations is non-linear.

Use of mechanical tests to predict durability of polymer fuel cell membranes under humidity cycling

A mechanical fatigue life analysis of the type used for lifetime predictions in structural materials has been adapted to characterize PEM fuel cell membranes. It is shown that a stress vs. cycles-to-failure ( S– N) curve analysis is capable of: (1) predicting the mechanical durability of PEM membranes under humidity cycling, and (2) assessing the fraction of membrane life remaining in degraded MEAs. Mechanical fatigue testing was performed in a dynamic mechanical analyzer (DMA) at 60 °C and 90% relative humidity (RH) under different values of stress amplitude, and the results were used to plot the S– N curve. The stress amplitude for the S– N curve was then mapped to the equivalent change in RH as a methodology for characterizing membrane mechanical resistance to humidity cycling.

Open Screw Fixation Versus Arthroscopic Suture Fixation of Tibial Posterior Cruciate Ligament Avulsion Injuries: A Mechanical Comparison

The objective of this study was to compare an arthroscopic suture technique with an open posterior screw fixation technique, by use of mechanical testing, for the treatment of posterior cruciate ligament (PCL) tibial bony avulsion. We split 10 intact human cadaveric knee pairs (20 knees) into 2 groups (A and B) with 1 knee from each pair and mounted them in a conventional tensile tester (Kratos 5002 Universal Biomechanical Test Machine; Kratos Dynamômetros, São Paulo, Brazil). By applying a posterior tibial load up to 100 N at 90 degrees of flexion, tibial displacement and stiffness were recorded. After a simulated PCL tibial avulsion fracture, the knees underwent PCL reattachment, with open screw fixation in group A and arthroscopic suture fixation in group B. The tests were performed first on intact and then on injured and operated knees. A direct visual inspection was performed postoperatively on all operated knees after a posterior arthrotomy to verify the fixation integrity. One knee in each group had a fixation failure on visual inspection. Analysis of variance testing showed no differences between groups A and B for tibial posterior displacement (P = .229) and stiffness (P = .285) analysis. The arthroscopic PCL tibial avulsion suture technique that we present is as reliable as open screw fixation for this lesion in terms of initial fixation. Various PCL avulsion surgery techniques have been reported, including alternatives to avoid potentially injurious exposure of the popliteal fossa. Following on this research line, we present a new arthroscopic suture for the treatment of this lesion that requires no special surgical skill or materials.

The cohesive mechanical properties of a toughened epoxy adhesive as a function of cure level

The cohesive performance of an epoxy adhesive as a function of cure applied is evaluated through the use of mechanical testing, thermal analysis and electron microscopy techniques. These material characterisation techniques allow a complete analysis of the reference material in terms of mechanical behaviour, surface topography and thermally induced events during cure. The effect of cure level within the adhesive was explored by examining all the material properties as a function of post cure duration and temperature. Post cure temperature and duration were both found to be directly proportional to the amount of curing reactions taking place within the system, with increases in post cure duration found to lower the temperature required to cure to a specific level. The mechanical properties of the adhesive varied as a function of post cure harshness with a number of mechanisms contributing to the strength during the post cure. The elastic modulus of the material was found to decrease with increases in post cure temperature, more so than with increases in post cure duration. Large increases in ductility were witnessed at certain post cure levels for each mode of loading. As curing levels are increased the glass transition temperature increases, until a point where the energy required to cause the transition then falls and the T g is lowered. The morphology of the toughening phase has also been characterised with spherical elements ranging from approximately 0.06 to 0.75 μm, and inter-phase spacing also noted along with the distribution of the elements. Basic mechanical testing of the adhesives was carried out in the form of lap shear and T-peel testing upon mild steel substrates, the correlation with glass transition temperature being stronger in these modes.

Development of metal-bonding spray adhesives for use in aerospace repair applications

In many aerospace applications, the use of film and paste adhesive materials is not conducive to either good manufacturability or good bonding properties. To address this concern, the development of high-performance, epoxy-based, spray-adhesive resins has been undertaken from a research and development standpoint. These materials were investigated in the light of their potential repair applications, with focus on adhesive joint designs based on lap-shear performance and processibility of the adhesive. It was found that the resins investigated displayed adequate lap-shear strengths for the bond types of interest. However, some resins proved to be a considerable challenge during processing and solvent removal presented a problem for some materials. As expected, the combined use of mechanical testing and scanning electron microscopy revealed that the lap-shear strengths of the resins could be tailored with changes in their chemistry, and that these changes also affected the solvent removal process.

Development of mechanical tests for stress corrosion and fatigue corrosion studies

Two specific examples are presented to describe the experience gained in the use of mechanical tests for the study of stress corrosion cracking and corrosion-fatigue: 1) the design of tension test platforms and low-frequency fatigue machines, having cross-head displacement rates of the order of 1 μm/h; 2) the use of curved tension test pieces to take into account heterogeneities of the material microstructure, in the case of cracking phenomena in burried pipelines.

Strains in extra-low-carbon steel sheets after weak (skin-pass) rolling

If not used within a few days of the last skin pass, low- and extra-low-carbon steel coils often give formed parts with stretcher-strain markings. These defects are caused by the phenomenon of strain aging occurring within the metal. By the use of mechanical tests, such as hardness and tensile tests, it is possible to follow the way in which the strength and ductility of the steel vary with time. X-ray diffraction studies were also conducted and gave results that do not appear to be influenced by the displacement of interstitial elements, but reveal compressive strains perpendicular to the sheet, and enable an average root mean square displacement of the atomic planes in question and an average dislocation density to he estimated. By considering the absolute plastic deformation imposed on the individual steel grains, it might be possible to link the random variation of the stresses with the distribution of dislocations. There may also be a connection between the stored plastic energy and the absolute plastic deformation.

The use of mechanical tests in determining the structure of connective tissues.

The use of mechanical tests in determining the structure of connective tissues.

194. The use of mechanical tests in the study of the structure of thin sheets of metal: M. Gourceaux, C. R. Acad. Sci. Paris, 254 (10), 5 March 1962, 1789–1790

194. The use of mechanical tests in the study of the structure of thin sheets of metal: M. Gourceaux, C. R. Acad. Sci. Paris, 254 (10), 5 March 1962, 1789–1790

The use of mechanical tests in the design of bituminous road surfacing mixtures. II. Stability tests on rolled asphalt

AbstractA comparison of resistance to deformation of rolled asphalt has been made at 45° using eight mechanical tests. The compositions tested conformed to B.S.594 and the comparison showed that these cover a wide range of stability. Some rich plastic mixtures included in B.S.594, although rejected after mechanical tests, can be used successfully on the road. Dynamic loading tests employing préssures experienced on the road appear to give the best relative assessment of stability for the compositions best suited to conditions in Great Britain.